Replacing Stock Sized Tire (1 Viewer)

[mooneywa]

I replaced my stock tires on my '15 with stock BFG AT KO2s. Straight size for size. I have close to 20k miles on them now. I drive around town, have done two Houston to Jackson Hole trips, multiple trips around Texas, and a lot of regular road driving.

The upsides: in the dirt and snow they are fantastic and the mileage penalty has been relatively minimal (.5mpg - to 1mpg total highway loss sometimes I don't even think there is much of a loss), the noise was better than expected.

The downsides: tread noise has increased especially after the 12k mile point. I rotate every 5k and I typically run 38-40 psi cold and have seen 0 issues with improper wear. They aren't mud terrain-like noise by any stretch but you're not going to keep dead quiet with them - maybe I just feel like it takes away some from the overall silence on the road I"d otherwise find in the cruiser. Let me emphasize, it's a small complaint.

In Jackson in the snow they were unstoppable without turning on any other aids. A foot of snow on unplowed roads and they just went. In the summer they let me hit up some pretty rocky trails without concern. Overall though? Probably more than I need. I might be hard pressed to get them again in place of Michellin AT2s? Although I bought a KO2 for a spare so I'll probably just buy 3 when the time comes and stay with what I have.

 

[Dan Higgins]

Yes. All LT-metric tires of the same size require the same pressure. For example, ALL LT285/70R17 tires on a LC200 require 40psi F/R. It doesn't matter who made the tire - BFG, Nitto, Falken, Cooper, etc. - if the tire is LT285/70R17 it requires 40psi F/R on a LC200.

It's all about the fact that tire manufacturers build tires to a standard set of specifications.

Load Rating - e.g. C, D or E - does not matter. At any given pressure, LT-metric tires of the same size will have the exact same Load Limit whether they are C-Rated, D-Rated or E-Rated. For example, ALL LT285/70R17 tires have a Load Limit of 2,315 pounds when inflated to 40psi. This is the same whether the tire is C-Rated, D-Rated or E-Rated. What changes is the Load Index for the differently rated tires.

Actual load always "matters," the question is what is the effect of a change in actual load. Put the same tire on a different vehicle and the actual load changes as does the recommended pressure. As far as Toyota is concerned, the recommended cold tire inflation pressure is correct for all vehicle loads up to the GVWR/GAWR numbers for that vehicle. In our case, for the LC200 the recommended cold tire inflation pressure is the same with or without a trailer, lightly loaded or fully loaded, as long as the specified loads (e.g. GVWR(7385lb), GAWR(3595lb Front, 4300lb Rear), GTW(8100lb), GCWR(14400lb), etc.) are not exceeded. Of course, we are free to increase tire pressure as a matter of personal preference up to the maximum indicated on the tire.

HTH

Thanks for the explanation. As I think about it, were we to replace the P-rated OEM tires with any other P-rated tires we are supposed to always use the PSI recommendations on the door jam.

I also wonder, though, were I to find 40 or even 38 PSI to be a bit more comfortable with the LT 285/65R18s, what would the downside be? Faster or uneven wear? Possible or absolute? Would I have less control on the road? Compared to the "softer" stock tires?

 

[gaijin]

Thanks for the explanation. As I think about it, were we to replace the P-rated OEM tires with any other P-rated tires we are supposed to always use the PSI recommendations on the door jam.

I also wonder, though, were I to find 40 or even 38 PSI to be a bit more comfortable with the LT 285/65R18s, what would the downside be? Faster or uneven wear? Possible or absolute? Would I have less control on the road? Compared to the "softer" stock tires?

If you inflate LT285/60R18 tires to 38-40psi instead of the recommended 46psi, just think about the downsides of underinflating any tire.

- At 40psi you would be 216 pounds/tire below the required Load Limit. This is unsafe. Absolute.
- Worse gas mileage. Absolute.
- Worse handling = less control on the road. Absolute.
- Uneven tire wear - usually showing greater wear on the outer tread areas. Dependent on tire design, but more probable or absolute than possible.
- Higher tire temperatures. Absolute. Leading to possible tire failure. More probable or absolute than possible.

The recommended cold tire inflation pressure is usually a best compromise between many variables - handling, mileage, comfort - but one variable that is not a compromise is the load the tires must be able to carry. At 46psi these tires are capable and safe, at 38-40psi they are not capable and unsafe.

Lots of folks decide to overinflate tires in an attempt to increase gas mileage by decreasing rolling resistance with what they deem acceptable trade-offs in comfort, handling and performance. I don't agree with this practice, but it is arguably not terribly unsafe. Underinflation is not safe under any circumstances.

Obviously, it is up to you what value you assign to comfort; but is safety for you, your family and others on the road really a smart trade-off?

HTH

 

[Dan Higgins]

Sorry. Just to clarify, I was referring to my 285/65R18s which, IIRC, you told me to put at 42 cold. I was talking about dropping them from 42 to 39-40 when "unloaded" (1 or 2 passengers, no luggage, etc.). Most of the time my LC weights about 6400. I would put them back at 42 if I am loading up for a trip or towing the trailer and approaching 7,000.

 

[gaijin]

Sorry. Just to clarify, I was referring to my 285/65R18s which, IIRC, you told me to put at 42 cold. I was talking about dropping them from 42 to 39-40 when "unloaded" (1 or 2 passengers, no luggage, etc.). Most of the time my LC weights about 6400. I would put them back at 42 if I am loading up for a trip or towing the trailer and approaching 7,000.

Sorry, didn't notice the thread switched sizes on me.

Still a bad idea to go below the recomended pressure. Going down to 39-40psi from 42psi doesn't sound like much(116 pounds/tire less load carrying capacity), and your rationale of lower weight should be OK with lower pressure sounds good on the face of it, but tire performance is more than just the capacity to hold a static load - live loading also needs to be accounted for. Basically, imagine hitting a pot hole with an underinflated tire. Regardless of the lower than max load of the vehicle, dynamic loads on the tire and wheel are much greater than just rolling down a smooth road. Without the full recommended pressure in the tire, the entire wheel/tire/suspension system is compromised and at greater risk of failure. The same concerns with high speed cornering and vehicle stability. Further, at reduced pressure there will be higher rolling resistance resulting in worse fuel mileage.

Above all, safety should be a primary concern.

If the tires are supposed to be at 42psi, then they should be at least that even under lighter load conditions.

HTH

 

[Dan Higgins]

Got it.

 

[Kgillkehoe]

I just recently replaced my stock Bridgestones with the general grappler at 2’s stock size and have really liked them!!!

 

[Kgillkehoe]

I just recently replaced my stock Bridgestones with the general grappler at 2’s stock size and have really liked them!!!

Thinking about putting them on my wife’s gx460 cause they’re so nice

 

[JS22STL]

I just recently replaced my stock Bridgestones with the general grappler at 2’s stock size and have really liked them!!!

How's road noise and ride on highway?

 

[kwatty]

So I got a flat in the stock tires at 30K miles and had the dealer replace all 4 with ko2 lt285/60r18. Just picked it up today. Per the tpms 1 rear is 38, one rear is 41, the fronts are 39 and 41. Haven’t manually checked the pressure but I will tomorrow. As I understand from reading this and other threads, 46 is the recommended pressure for this tire. So how does a dealer not know this? And on top of that can’t even match the pressures from tire to tire.

 

[TeCKis300]

Sorry, didn't notice the thread switched sizes on me.

Still a bad idea to go below the recomended pressure. Going down to 39-40psi from 42psi doesn't sound like much(116 pounds/tire less load carrying capacity), and your rationale of lower weight should be OK with lower pressure sounds good on the face of it, but tire performance is more than just the capacity to hold a static load - live loading also needs to be accounted for. Basically, imagine hitting a pot hole with an underinflated tire. Regardless of the lower than max load of the vehicle, dynamic loads on the tire and wheel are much greater than just rolling down a smooth road. Without the full recommended pressure in the tire, the entire wheel/tire/suspension system is compromised and at greater risk of failure. The same concerns with high speed cornering and vehicle stability. Further, at reduced pressure there will be higher rolling resistance resulting in worse fuel mileage.

Above all, safety should be a primary concern.

If the tires are supposed to be at 42psi, then they should be at least that even under lighter load conditions.

HTH

Gaijin, hope you don't take this as challenging you but I'm curious.

Tire loads always take in to account speed. How does that play into your position?

For example, speed limits on cars are highly correlated to the stock tire fitment top speed capability. Tire loads and the heat generated are generally the most extreme at that top speed. If we were to accept that we might drive at lower than top speed, could we also run less PSI?

Case in point is off-roading. We all routinely air down, way down at that, for better performance to irregularities off road. Part of the understanding is that we also, in general, run much lower speeds. And while the tire sidewalls are surely getting exercised more (and heating up more), this is still somewhat an accepted practice?

 

[gaijin]

Gaijin, hope you don't take this as challenging you but I'm curious.

Tire loads always take in to account speed. How does that play into your position?

For example, speed limits on cars are highly correlated to the stock tire fitment top speed capability. Tire loads and the heat generated are generally the most extreme at that top speed. If we were to accept that we might drive at lower than top speed, could we also run less PSI?

Case in point is off-roading. We all routinely air down, way down at that, for better performance to irregularities off road. Part of the understanding is that we also, in general, run much lower speeds. And while the tire sidewalls are surely getting exercised more (and heating up more), this is still somewhat an accepted practice?

Don't worry, I'll keep this short ...

Maximum safe speed limit on our vehicles when fitted with All-Terrain type LT-Metric tires is in nearly all cases limited by the Speed Rating of the tire which is fitted. In the case of my 2013 LC200 with LT285/70R17E 121/118R tires, the maximum safe speed limit is determined by the "R" Speed Rating - 106 mph. The Recommended Cold Tire Inflation Pressure for these tires is 40psi which assures the required load bearing capacity for the tires at all speeds up to the maximum of 106 mph.

Whatever heat gain a tire has above ambient is caused by the flexing of the sidewall (we are not racing the Daytona 500 with our vehicles, so I ignore heat gain caused by near constant high speed side slipping experienced by race cars on race tracks due to understeer, oversteer or both). The more flex, the more heat gain. A properly inflated tire may well experience more heat gain at lower speeds than at higher, i.e. highway, speeds than at lower speeds because of the dimensional change of the tires at speed. Also, heavier loads will usually result in more sidewall flex and thus more heat gain.

So, first point, even if we were to travel only at lower than top speed, no, we cannot run less psi. Lower psi would increase tire sidewall flex, increase heat gain, reduce load carrying ability and reduce resistance to transient live loading increases due to hitting obstructions like potholes and speed bumps, curbs, or unanticipated emergency maneuvers.

Tire pressure, in combination with vehicle weight, determine the "spring rate" of a tire. This has nothing to do with the metal springs elsewhere in the suspension system, but rather refers to the rate at which the tire itself will compress and rebound in reaction to transient loading spikes. More pressure, stiffer tire; less pressure, softer tire. No surprise, right? So, even at lower than top speed, running on tires with a softer than spec "spring rate" would result in potentially dangerous handling, less precise steering, increased braking distance, lower gas mileage, etc., etc.

Off-roading is a special use case in which a tire's load carrying capacity and durability are purposely jeopardized in favor of increased traction/floatation to suit existing conditions. Yes, it is accepted practice to air down for very slow speed off-road use, but it is also accepted practice to air up again to the Recommended Cold Tire Inflation Pressure when returning to "normal" driving speeds on road.

Does that answer your question?

HTH

 

[kwatty]

So how does one find the recommended pressure for any given tire? So it is definitely 46 for Lt285/60r18? The dealer installed them and left them at 40psi. What would be their reasoning (or lack thereof) for that? Thanks a lot.

Good question - and an easy answer.

ALL P285/60R18 tires on a LC200 have a recommended Cold Tire Inflation Pressure of 33psi F/R.

ALL LT285/60R18 tires on a LC200 have a recommended Cold Tire Inflation Pressure of 46psi F/R.

Vendor and Load Rating have no effect on the recommended pressure. For LT tires specifically, it makes no difference if the tire is C-Rated, D-Rated or E-Rated - if they are the same size, they require the same pressure.

Recommended pressures are different for LX570's.

HTH

 

[kwatty]

BF Goodrich customer support just advised me to use 50psi for lt285/60rt18.

 

[gaijin]

So how does one find the recommended pressure for any given tire? So it is definitely 46 for Lt285/60r18? The dealer installed them and left them at 40psi. What would be their reasoning (or lack thereof) for that? Thanks a lot.

Yes, the Recommended Cold Tire Inflation Pressure for LT285/60R18 tires on a 200 Series Land Cruiser is 46psi Front/Rear.

The dealer is wrong and 40psi is underinflated. Their reasoning? They just guessed - and they guessed wrong.

The Tire and Rim Association (TRA) works with the federal government, tire and rim manufacturers, vehicle manufacturers and airplane manufacturers to establish standards for tires and rims. One of these standards is the Load Limit / Inflation tables which establish the Load Limit each size tire must exhibit at any given Cold Tire Inflation Pressure. You can read more about the TRA here: The Tire and Rim Association, Inc.

Usually, one must purchase the TRA Yearbook (which I did) to access the complete Load/Inflation tables, but Toyo Tire did us all a favor and published an excellent guide to using the TRA tables which includes most of the relevant tables. You can find the Toyo Guide here: https://toyo-arhxo0vh6d1oh9i0c.stac...ication_of_load_inflation_tables_20170203.pdf

I suggest you read the entire Toyo Guide, this will tell you exactly how one determines the recommended pressure for any tire size not listed on the information placard located on the door jam. Basically, one determines the Load Limit required by the vehicle manufacturer for the stock tires supplied with the vehicle - for the LC200, that is 2,512 pounds for the stock P285/60R18 tires. If replacing P-Metric tires with LT-Metric tires, one needs to adjust the recommended pressure Load Limit by 10%, so for LT-Metric tires, the required Load Limit is 2,512 pounds / 1.1 = 2,284 pounds. Then one looks in the Load/Inflation tables for the LT285/60R18 tires (see page 23 of the Toyo Guide). You will find that for that tire, the required 2,284 pounds Load Limit lies somewhere between 45psi (2,250 pounds) and 50psi (2,470 pounds). Some manufacturers and tire dealers simply round up to 50psi and use that, but to determine the closest single psi value for tire inflation, you can calculate 2,470 - 2,250 = 220 pounds. Since there are 5psi between those two values, 220/5=44psi ... so you can add 44 pounds of Load Limit per psi between 45 and 50 psi to reach the closest value above the required 2,284 pounds. In this case it is 2,250 pounds (45psi) + 44 pounds (1psi) = 2,295 pounds (46psi).

Simple, right?

HTH

 

[gaijin]

BF Goodrich customer support just advised me to use 50psi for lt285/60rt18.

They simply rounded up to the next whole value listed in the tables without doing the calc to refine the answer to 46psi. This covers their collective corporate a***s by only recommending exactly numbers included in the TRA tables.

HTH

 

[kwatty]

Yes, the Recommended Cold Tire Inflation Pressure for LT285/60R18 tires on a 200 Series Land Cruiser is 46psi Front/Rear.

The dealer is wrong and 40psi is underinflated. Their reasoning? They just guessed - and they guessed wrong.

The Tire and Rim Association (TRA) works with the federal government, tire and rim manufacturers, vehicle manufacturers and airplane manufacturers to establish standards for tires and rims. One of these standards is the Load Limit / Inflation tables which establish the Load Limit each size tire must exhibit at any given Cold Tire Inflation Pressure. You can read more about the TRA here: The Tire and Rim Association, Inc.

Usually, one must purchase the TRA Yearbook (which I did) to access the complete Load/Inflation tables, but Toyo Tire did us all a favor and published an excellent guide to using the TRA tables which includes most of the relevant tables. You can find the Toyo Guide here: https://toyo-arhxo0vh6d1oh9i0c.stac...ication_of_load_inflation_tables_20170203.pdf

I suggest you read the entire Toyo Guide, this will tell you exactly how one determines the recommended pressure for any tire size not listed on the information placard located on the door jam. Basically, one determines the Load Limit required by the vehicle manufacturer for the stock tires supplied with the vehicle - for the LC200, that is 2,512 pounds for the stock P285/60R18 tires. If replacing P-Metric tires with LT-Metric tires, one needs to adjust the recommended pressure by 10%, so for LT-Metric tires, the required Load Limit is 2,512 pounds / 1.1 = 2,284 pounds. Then one looks in the Load/Inflation tables for the LT285/60R18 tires (see page 23 of the Toyo Guide). You will find that for that tire, the required 2,284 pounds Load Limit lies somewhere between 45psi (2,250 pounds) and 50psi (2,470 pounds). Some manufacturers and tire dealers simply round up to 50psi and use that, but to determine the closest single psi value for tire inflation, you can calculate 2,470 - 2,250 = 220 pounds. Since there are 5psi between those two values, 220/5=44psi ... so you can add 44 pounds of Load Limit per psi between 45 and 50 psi to reach the closest value above the required 2,284 pounds. In this case it is 2,250 pounds (45psi) + 44 pounds (1psi) = 2,295 pounds (46psi).

Simple, right?

HTH

That’s awesome. Thank you very much. I will put them at 46. I really appreciate it.

 

[TeCKis300]

Don't worry, I'll keep this short ...

Maximum safe speed limit on our vehicles when fitted with All-Terrain type LT-Metric tires is in nearly all cases limited by the Speed Rating of the tire which is fitted. In the case of my 2013 LC200 with LT285/70R17E 121/118R tires, the maximum safe speed limit is determined by the "R" Speed Rating - 106 mph. The Recommended Cold Tire Inflation Pressure for these tires is 40psi which assures the required load bearing capacity for the tires at all speeds up to the maximum of 106 mph.

Whatever heat gain a tire has above ambient is caused by the flexing of the sidewall (we are not racing the Daytona 500 with our vehicles, so I ignore heat gain caused by near constant high speed side slipping experienced by race cars on race tracks due to understeer, oversteer or both). The more flex, the more heat gain. A properly inflated tire may well experience more heat gain at lower speeds than at higher, i.e. highway, speeds than at lower speeds because of the dimensional change of the tires at speed. Also, heavier loads will usually result in more sidewall flex and thus more heat gain.

So, first point, even if we were to travel only at lower than top speed, no, we cannot run less psi. Lower psi would increase tire sidewall flex, increase heat gain, reduce load carrying ability and reduce resistance to transient live loading increases due to hitting obstructions like potholes and speed bumps, curbs, or unanticipated emergency maneuvers.

Tire pressure, in combination with vehicle weight, determine the "spring rate" of a tire. This has nothing to do with the metal springs elsewhere in the suspension system, but rather refers to the rate at which the tire itself will compress and rebound in reaction to transient loading spikes. More pressure, stiffer tire; less pressure, softer tire. No surprise, right? So, even at lower than top speed, running on tires with a softer than spec "spring rate" would result in potentially dangerous handling, less precise steering, increased braking distance, lower gas mileage, etc., etc.

Off-roading is a special use case in which a tire's load carrying capacity and durability are purposely jeopardized in favor of increased traction/floatation to suit existing conditions. Yes, it is accepted practice to air down for very slow speed off-road use, but it is also accepted practice to air up again to the Recommended Cold Tire Inflation Pressure when returning to "normal" driving speeds on road.

Does that answer your question?

HTH

Fair answer. Mostly consistent with how I understand things. Though I still tailor my inflation pressure from the recommended pressure at times based on what my use case is. Generally, that is to go higher than recommended for added load, either hauling loads with my SUV, or putting my sports car on the track. I find the recommended PSI's a good balance between ride and handling. Any less, and handling gets too sloppy for my personal tastes.

Thanks for taking the time!

 

[jsuthey]

Lots of good info here but can we please see some pics of stock size (285/60-18) BFG KO2's!! Not trying to hijack just thought it would help OP.I'm going to replace stock tires very soon and I am interested.Better yet next size up(285/65-18) pics.I think I should start my own thread as I'm on the fence for both sizes.Really what it comes down to is convincing my wife,she wants pics also!

 

[drmwvr]

I’m the OP and I went with stock sized KO2s. I think it looks really good..I’ll try to get some better pics later in the week but here is one from my garage.